Barkskin

Level & School
2nd-level transmutation
Casting Time
Bonus action
Range
Touch
Components
V, S, M (a handful of bark)
Duration
1 hour
Classes
Druid, Ranger

You touch a willing creature. Until the spell ends, the target's skin assumes a bark-like appearance, and the target has an Armor Class of 17 if its AC is lower than that.

Level & School
2nd-level transmutation
Casting Time
Action
Range
Touch
Components
V, S, M (a handful of oak bark)
Duration
Concentration, 1 hour
Classes
Druid, Ranger

You touch a willing creature. Until the spell ends, the target's skin has a rough, bark-like appearance, and the target's AC can't be less than 16, regardless of what kind of armor it is wearing.

Barkskin 5.5e 2024 vs. 5e 2014 edition differences

The 2024 version sets the target's AC to 17 if lower, replacing the 16 minimum AC in 2014; it also changes the casting time from an action to a bonus action. The effect description is slightly different but mechanically similar otherwise.